The present invention relates generally to printing methods and apparatus, and particularly relates to ink drying as applied in the context of inkjet printing operations.
Inkjet printing produces print imaging by propelling ink droplets onto media. A variety of inkjet printing apparatus have evolved, but generally share in the common characteristic of rendering an image by depositing liquid on a media substrate. As such, inkjet printing methods and operations sometime include or even require drying of media, i.e., drying liquid ink following application to media as print imaging.
Inkjet drying techniques include passing media including wet print imaging through heated rollers. Unfortunately, the application of heat energy and consequent drying to wet media when in a curved condition, i.e., as wrapped around a roller, often results in undesirable cockling and/or buckling or curvature of output. As a result, such media often suffers in quality and in some cases requires additional processing to xe2x80x9cflattenxe2x80x9d the media.
Use of microwave drying in an inkjet printing process is known. For example, U.S. Pat. No. 5,220,346 issued Jun. 15, 1993 and entitled Printing Process With Microwave Drying illustrates ink formulations and use of a microwave drying as applied in the context of inkjet printing. U.S. Pat. No. 5,563,644 issued Oct. 8, 1996 to Isganitis et al. and entitled Inkjet Printing Process with Microwave Drying also shows use of microwave radiation to dry ink in an inkjet printing context.
Generally, application of heat energy to wet ink volatilizes the ink and thereby dries print imaging produced thereby. Unfortunately, volatizing ink produces ink vapor which undesirably contaminates a printing operation and inhibits further drying. More particularly, volatilized ink compounds should be carried away from a printing operation so as to prevent excessive buildup of such compounds as volatilized or as settling back into liquid form. Thus, many ink drying methods and apparatus must carry away volatized ink compounds so as to avoid contamination of the printing operation. Accordingly, many ink drying methods and apparatus employ a separate system for carrying away and suitably venting volatized ink compounds. Volatilized ink compounds also inhibit further drying when accumulated at the media surface. In other words, volatized ink compounds tend to accumulate at a xe2x80x9cboundary layerxe2x80x9d of the media surface. This body of volatilized ink tends to prevent further volatilization of ink and thereby either inhibit or completely stop further drying of print imaging. Accordingly, ink drying methods and apparatus often xe2x80x9cscrubxe2x80x9d this boundary layer to remove a body of volatilized ink compounds from the media surface and thereby promote further productive drying of print imaging.
The present invention combines microwave heating apparatus and techniques with airflow techniques to improve overall ink drying in an inkjet printing operation. Microwave drying techniques, while effective, produce at the media surface a xe2x80x9cboundary layerxe2x80x9d of vaporized ink inhibiting or significantly impairing further productive drying thereat. The present invention incorporates airflow pathways within a microwave applicator to scrub this boundary layer and thereby promote more efficient drying by microwave radiation. In addition, the present invention, through use of selected air pathways in and about a heat zone, takes away undesirable ink vapors produced by the drying process and thereby eliminates need for separate apparatus dedicated specifically to ink vapor removal.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation of the invention, together with further advantages and objects thereof, may best be understood by reference to the following description taken with the accompanying drawings wherein like reference characters refer to like elements.